What originally pushed me toward Recurly was that they support VAT (and I run a french company) - plus Stripe wasn't available back then in France either :-) Currently adding VAT support to Stripe is fairly complex (based on what people who implemented it told me), you basically have to do everything yourself and add custom line items via invoice callbacks.
I hope they will support more VAT at some point!
I will try to make a more educated comparison later on though.
Really wanted to thank you for the link to the Koudoku gem and for sharing more online; the more we have information on how to implement SaaS services, the more developers will be empowered to start businesses.